Hagfish? Sorry Greame, I explain:According to D. Quicke's glossary:Cyclostome: having a cavity above the mandibules formed by the recession of the lower part of the clypeus and exposure of the often concave labrum; usually dorsally rounded.You can see an illustration on this page (in paragraph Can you see the difference?)Some cyclostome Braconidae subfamilies: Braconinae, Doryctinae, Alysiinae, Rogadinae, Opiinae...Some non cyclostome Braconidae subfamilies: Microgastrinae, Cheloninae, Euphorinae, Agathidinae, Blacinae, Macrocentrinae, Helconinae ...

I will jump in and say this is the subfamily Braconinae. In the Nearctic region, the two most common genera with this gestalt are Bracon and Habrobracon, so I wouldn't be surprised if your beast turns out to be one of those.